Fuel injector

ABSTRACT

A unit fuel injector having metering means incorporated in the pumping element of the injector.

United States Patent Gayfer July 1, 1975 FUEL INJECTOR [56] References Cited [75] Inventor: John Roland Gayfer, Alcester, UNITED STATES PATENTS England 2,558,148 6/1951 Nichols 239/574 D 2,959,360 11/1960 Nichols 239/533 [73] fi s" S 324L768 3/1966 Croft 239/533 x 3,233,379 11/1966 Croft 61 al. 2 239/533 x [22] June FOREIGN PATENTS OR APPLICATIONS pp 484,111 746,785 3 1956 United Kingdom .1 239/533 [30] Foreign Application Priority Data Primary ExaminerflR'oben S: l

June 30, 1973 United Kingdom 2 31262/73 Agent & Kruger [52] US. Cl 5 239/533; 239/574 AB TR CT [5 1 1 1 v 1 v 1 A unit fuel injector having metering means inco po [58] Field of Search 1. 239/5 33, 574, 88-91, rated i the pumping den-lent f the injectorv 5 Claims, 3 Drawing Figures PATEmEn uL'nsrs SHEET 7/////// 1 V \N\ w a R ///////%//7 A common system of'fuel injection for diesel engines utilises a central pump which operates to meter a given quantity of fuel, distribute it, perform any necessary governing function and finally feed the fuel by way of a high pressure pipe to the injector for a given cylinder. In such a system the injector is a simple snap-action valve.

A major disadvantage of the described central high pressure pump system lies in the volume of the fuel col umn trapped in the distribution pipes between pump and a given injector. The trend towards higher maximum speeds for small diesel engines is causing the elasticity and inertia of the fuel column to degrade injection accuracy.

According to the present invention there is provided a fuel injector comprising:

a. a body member incorporating a fuel inlet, and a fuel outlet nozzle communicating with a bore by way of a plenum chamber;

b. a needle slidably disposed within the bore between a first position in which the outlet nozzle is closed and a second position in which the outlet nozzle is open;

c. biassing means resiliently loading the needle towards the first position;

d. a metering plunger in a plunger bore in the needle;

e. pressure sensitive means operable to isolate the plenum chamber from fuel inlet; and

f. a metering plunger displacing means operable:

i. to cause the pressure sensitive means to isolate the plenum chamber from fuel inlet;

ii. to pressurise fuel within the plenum chamber to the extent necessary to cause displacement of the needle from the first to second position against the action of the biassing means and allow output from the nozzle of a given amount of fuel from the plenum chamber.

ln a first preferred form of the invention the metering plunger displacing means comprises a solenoid adapted to vary the metered quantity of fuel from the plenum chamber by varying the stroke length of the plunger.

ln a second preferred form of the invention the metering plunger displacing means is a solenoid adapted to vary the metered quantity of fuel from the plenum chamber by varying the time for which the plunger is displaced for a fixed stroke length.

FIG. 1 is a sectional view of one embodiment of the invention;

FIG. 2 is a sectional view ofa second embodiment of the invention; and

FIG. 3 is a sectional view of a third embodiment of the invention.

All three figures show a body member 1] having a fuel inlet 12, and an outlet nozzle 13 communicating with a bore 14 by way of a plenum chamber 15. The bore 14 contains a needle 16 which is shown in a first position closing the outlet nozzle. The needle 16 is slidable to a second position in which fuel in plenum chamber is free to flow out of the nozzle. The needle contains a plunger bore 17 in which plunger 18 is slidable. The body member I] is mounted in an engine block to position the nozzle 13 in a cylinder head combustion chamber.

Each figure will now be considered separately.

FIG. 1

The needle 16 encloses a chamber 20 and transfer ducts 21 (only two being shown). The needle has a pintle shaped end 22 with inclined face 23 and tapered portions 24, 25. lnlet ports 26 align with annulus 27 fed by inlet 12. The upper end of the needle has seated on it a ring flange 28 which is resiliently loaded by a spring washer 29 to bias the needle to seat tapered portion 24 onto, and so close, nozzle 13. The spring rate is chosen to allow the needle 16 to rise under the force exerted on the tapered end of the needle by pressurised liquid fuel in plenum 15.

Plunger 18 has a passage 30 extendng through it coaxial with plunger 18 and needle 16. The plunger 18 has ports 31 alignable with ports 26. The plunger is driven from its upper end by a first solenoid.

Valve head 32 serves to close the bottom end of passage 30 and is mounted on the lower end of stem 33. The valve stem 33 is driven from its upper end by a second solenoid.

In operation diesel fuel is fed to fuel inlet 12 at a pressure selected to fill chamber 20 within a permitted time. With the parts in the relative dispositions shown in FIG. 1 fuel passes through ports 26, 31 into passage 30. Thereafter the second solenoid drives valve stem 33 to lift head 32 clear of its seating at the bottom of passage 30 so allowing fuel to pass into chamber 20. The first solenoid is then energised to drive plunger 18 downwardly over a fixed stroke length to reduce the volume of chamber 20 so pressurising fuel contained in the chamber 20, ducts 21 and plenum chamber 15. When fluid pressure acting on the inclined face 23 of the needle exceeds the resilient loading on flange 28, together with the load due to fluid pressure acting on the lower surface containing chamber 20, the needle 16 is raised so allowing fuel to be injected into and through nozzle 13 to the cylinder fed by the injector.

The embodiment described makes use of solenoids to drive valve stem 33 and the plunger 18. The plunger 18 operates on a fixed stroke length so that fuel metering is governed by the period for which head 32 is open to allow the passage of fuel.

FIG. 2

The needle 16 encloses a chamber 40 and transfer ducts 41. lnlet annulus 42 is fed by fuel inlet 12. The upper end of needle 16 has seated on it a flange 43 which is resiliently loaded by spring washer 44 to bias the needle end 45 to close nozzle 13. The rate of spring washer 44 is selected to allow needle 16 to rise under the force exerted on tapered end 46 of the needle 16 by pressurised fuel in plenum chamber 15.

Plunger 18 has a coaxial passage 47 extending through it which communicates with annulus 42 by way of cross-boring 48. The lower end of passage 47 is closable by a ball valve 48 which is resiliently biassed by coil spring 49. The plunger 18 is displaceable by a solenoid S0 to vary the volume of chamber 40 and so the pressurisation of fuel in chamber 40 and plenum chamber 15.

In operation diesel fuel is fed to fuel inlet 12 at a pressure selected to lift ball valve 48 clear of passage 47 and so allow fuel to fill chamber 40 (by way of annulus 42 and cross boring 48) within a permitted time. When the solenoid S0 is energised plunger 18 is driven downwardly causing ball valve 48 to seat on passage 47 and cut off chamber 40 from inlet 12. Further downward movement of the plunger pressurises fuel in chamber 40 and plenum until the fluid pressure is sufficient to lift needle 16 and allow fuel to be injected through nozzle 13 into the cylinder fed by the injector. ln this embodiment the stroke length of plunger 18 is governed by the solenoid so that the amount of fuel metered can be varied in response to engine load.

FIG. 3

The needle 16 encloses a chamber 60 and transfer ports 61. The needle has a pintle shaped end 62. The needle 16 has its upper end loaded by a spring washer in similar manner to that described in connection with FIGS. 1 and 2.

Plenum chamber 15 is linked directly to fuel inlet 12 by way of duct 63 containing ball valve 64 biassed by spring 65 to lie on seating 66 in which position fuel flow from inlet 12 to plenum 15 is cut-off.

Plunger 18 is driven from its upper end by a solenoid which can provide a variable stroke length of plunger movement. In operation pressurised diesel fuel is fed to plenum 15 by way of inlet 12 and duct 63. The fuel is sufficiently pressurised to lift ball valve 64 from seating 66. Energisation of the solenoid causes the plunger 18 to be driven downwardly to pressurise fuel in the chamber 60, plenum l5 and in the part of the duct 63 beneath ball valve 64 so causing it to seat and shut off further fuel flow into the plenum chamber 15. Further movement of the plunger will further pressurise fuel until the needle 16 lifts allowing fuel injection into the cylinder fed by the injector.

Reference is made in FIGS. 2 and 3 to a ball valve however any appropriate form of resiliently biassed stop valve can be used.

Although the embodiments specifically refer to the use of diesel fuel the injectors described can also be used for petrol.

I claim:

1. A fuel injector comprising:

a. a body member incorporating a fuel inlet, and a fuel outlet nozzle communicating with a bore by way of a plenum chamber;

b. a needle slidably disposed within the bore between a first position in which the outlet nozzle is closed and a second position in which the outlet nozzle is open;

c. biassing means resiliently loading the needle to wards the first position;

d. a metering plunger in a plunger bore in the needle;

e. pressure sensitive means operable to isolate the plenum chamber from fuel inlet; and

f. a metering plunger displacing means operable:

i. to cause the pressure sensitive means to isolate the plenum chamber from fuel inlet;

ii. to pressurise fuel within the plenum chamber to the extent necessary to cause displacement of the needle from the first to second position against the action of the biassing means and allow output from the nozzle of a given amount of fuel from the plenum chamber.

2. A fuel injector as claimed in claim 1 wherein the metering plunger displacing means comprises a solenoid adapted to vary the metered quantity of fuel from the plenum chamber by varying the stroke lengths of the plunger.

3. A fuel injector as claimed in claim 1 wherein the metering plunger displacing means comprises a solenoid adapted to vary the metered quantity of fuel from the plenum chamber by varying the time for which the plunger is displaced for a fixed stroke length.

4. A fuel injector as claimed in claim 1 wherein the pressure sensitive means comprises a resiliently biassed stop valve disposed in a duct linking the fuel inlet directly to the plenum chamber;

5. A fuel injector as claimed in claim 1 wherein the pressure sensitive means comprises a resiliently biassed stop valve disposed in a duct linking the fuel inlet to the plenum chamber by way of the plunger. 

1. A fuel injector comprising: a. a body member incorporating a fuel inlet, and a fuel outlet nozzle communicating with a bore by way of a plenum chamber; b. a needle slidably disposed within the bore between a first position in which the outlet nozzle is closed and a second position in which the outlet nozzle is open; c. biassing means resiliently loading the needle towards the first position; d. a metering plunger in a plunger bore in the needle; e. pressure sensitive means operable to isolate the plenum chamber from fuel inlet; and f. a metering plunger displacing means operable: i. to cause the pressure sensitive means to isolate the plenum chamber from fuel inlet; ii. to pressurise fuel within the plenum chamber to the extent necessary to cause displacement of the needle from the first to second position against the action of the biassing means and allow output from the nozzle of a given amount of fuel from the plenum chamber.
 2. A fuel injector as claimed in claim 1 wherein the metering plunger displacing means comprises a solenoid adapted to vary the metered quantity of fuel from the plenum chamber by varying the stroke lengths of the plunger.
 3. A fuel injector as claimed in claim 1 wherein the metering plunger displacing means comprises a solenoid adapted to vary the metered quantity of fuel from the plenum chamber by varying the time for which the plunger is displaced for a fixed stroke length.
 4. A fuel injector as claimed in claim 1 wherein the pressure sensitive means comprises a resiliently biassed stop valve disposed in a duct linking the fuel inlet directly to the plenum chamber.
 5. A fuel injector as claimed in claim 1 wherein the pressure sensitive means comprises a resiliently biassed stop valve disposed in a duct linking the fuel inlet to the plenum chamber by way of the plunger. 